The research program is directed toward expanding our studies of the structure and development of viruses and to correlate biochemical events with morphological changes occurring in infected cells. By use of specific ferritin-conjugated antibodies it has been possible to identify viral components before their assembly into mature virions. The replication of Herpes simplex, Sendai, influenza, vesicular stomatitis virus, adenovirus, and visna virus has been studied with this technique. Attention is now being directed toward investigation of the replicative cycle of Herpes saimiri. In addition, various cell lines, especially those of human origin, will be infected with Herpes saimiri in an attempt to produce malignant transformation. If successful, this will provide a model for investigation of the neoplastic process in animals. Studies of the development of herpesviruses, namely equine abortion virus, in vivo are continuing. In particular, emphasis is being placed on examining by electron microscopy the manner in which the defensive mechanisms of the host alter the infectious process.